The present invention describes an external counterpulsation device. More specifically, the present invention applies electroactive polymer actuators to an external counterpulsation device.
Exterior counterpulsation (ECP) is a technique in which the exterior of a patient's body is compressed (usually the extremities such as the legs) in synchrony with the heartbeat of the patient in order to assist the pumping action of the heart. ECP is established, for example, in critical care and cardiology units for treatment of heart failure and for the rescue of heart attack patients.
There are several current manufacturers of ECP systems. The current systems resemble a pair of trousers or support hosiery, and function in a way similar to that of a gravity garment used by pilots of certain aircraft. Pneumatic tubes are connected to the garment to compress the patient's extremities (usually the legs) in synchrony with the heartbeat. This assists the pumping action of the heart by forcing blood from the extremities by compressing the veins and relying on the venous valves to favor one-way flow, so the heart need not do all the work of perfusion. The resultant reduction in cardiac work allows normalization of blood flow and metabolism, reduces the otherwise destructive downward metabolic spiral, and allows the heart to rest and recover.
However, present ECP systems suffer from a number of disadvantages. As described above, the actuators in conventional ECP systems are traditionally pneumatic. Such actuators are typically rather large and bulky leading to a clumsy fit around the patient. The size and bulk of the actuators can also render them quite cumbersome and uncomfortable in attempting to fit them on a patient. In addition, the large pneumatic actuators are typically quite noisy and difficult to control. Also, they are relatively slowly acting. Therefore, they are difficult to control in precise synchrony with the heartbeat. Further, the actuators are quite expensive, mechanically inefficient, and require a bulky, complex pneumatic drive console.